CVE-2026-86099

Summary

Chainlit through 2.12.0 fails to validate the client-supplied socket.io sessionId parameter, allowing unauthenticated attackers to traverse filesystem paths by injecting absolute or relative path sequences. Attackers can craft malicious sessionId values that escape the upload directory and recursively delete arbitrary directories accessible to the service process.

Affected Software

Weaknesses

• CWE-22: CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: partial

References

• https://github.com/Chainlit/chainlit
• https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/session.py
• https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/socket.py
• https://pypi.org/project/chainlit/
• https://www.vulncheck.com/advisories/chainlit-through-2.12.0-path-traversal-via-socket-io-sessionid

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